Think about it this way, Rose and Lissa found it easier to be out in the human world. The real conflict of the story started when they had to return to the school, where they were judged by those around them. In a way, they were safer outside because nobody knew where they were, vs sitting at the school like a clear target.
Harry Potter might have been a much different novel if he'd been forced to attend a Muggle school. Harry wouldn't have learned to control his powers. He wouldn't have a wand.
He wouldn't know anything about Voldemort, etc, etc. So put some thought into it. Your setting can add or remove conflict. Think about what you need for the story.
Think about how each type of school will affect the characters and their goals.
Start writing a backstory for these girls, and if write whichever school fits the story.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.